Exhaust System 65 Mustang 347 Engine Swap

dvelek

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Jun 5, 2019
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Alvin, Texas
Pulling the 289 that is sick and dropping a 347 Crate here on the next couple weeks and need suggestions on exhaust systems to match the engine . I’m being told I need to go with a bigger diameter to increase the performance . Thanks for the help guys .
 
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geoklass

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Sep 3, 2018
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Bigger than what?

What cylinder heads do you have?
What transmission do you have?
How much power do you think your engine will make?
Is it a street car or a race car, or is it a street/strip car?

George
 

geoklass

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Sep 3, 2018
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With the T-10 transmission, are you using a cable clutch linkage, or a hydraulic clutch linkage, or the stock Z-Bar style clutch linkage? A lot of headers will not clear the Z-Bar set up, you need to check with CJ Pony Parts on that one. Also, you forgot to tell us what cylinder heads you are going to be using. The headers you listed (Tri-Y Headers) are okay for a street car, but the primary tubes are only 1 1/2" in diameter, which may be too small for a 347 inch engine. I would say that you need 1 5/8" primaries at least....

George
 

geoklass

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dvelek

Member
Jun 5, 2019
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Alvin, Texas
George appreciate the info and the cylinder head info is below.

BluePrint Aluminum Cylinder Heads -HP9008
60cc chamber
2.02" intake/1.60" exhaust valves
190cc intake/65cc exhaust runners
 

geoklass

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Sep 3, 2018
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Monrovia, California
Those heads are fine for a good running street machine. Note the exhaust valve size (1.60" diameter). This seems to be the standard for almost every aftermarket SB Ford cylinder head, regardless of brand. The important thing to understand is that 1.60" diameter is smaller around the 1 5/8" (1.625"). However, the exhaust does not go through a hole that is 1.60", it goes through the opening in the valve seat, which is about 1 1/2" in diameter, and in that 1 1/2" diameter, the exhaust valve stem is an obstruction that interferes with the exhaust flow. This makes an 1 3/4" header look huge as far as exhaust flow on any hot running street Mustang. The reality is that 1 5/8" headers are VERY adequate for any 400 to 450 HP SB Ford street machine...